Rheostat



May 1, 19.23. 1,453,682

Q L. KEBLER RHEOSTAT Filed Dec. .20, 1920 IIIIIIIIIHI l IIIHIIIIIHI mvewtoz WM 851 A elf musk i l iii Patented May 1, 1923.

uNiTEo STATES PATENT OFFICE.

LEONARD KEBLER, OF BRO'NXVILLE, NEW YORK, ASSIGNOR IO WARD LEONARD ELECTRIC COMPANY, A OURPORATION 033 NEW YORK.

BHEOSTAT.

Application filed December 20, 1820.

T 0 all whom it may concern:

Be it known that I, LEONARD KneLnR, a citizen of the United States, residing at Bronxville, in the county of lVestchester and State of New York, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

This invention relates to the type of rheostats, or resistance regulators, in which a rotatable contact arm moves over a series of contacts to which the resistance elements are connected, and thus varies the amount or resistance in the circuit controlled. The resistance contacts heretofore have been arranged on the arc of a circle and engaged by the outer end of the rotatable contact arm, the resistance elements extending outwardly from the circularly arranged contacts.

One object of the present invention is to provide 'a construction whereby the contact arm may have a large angular movement in passing from one limit of movement to the other limit of movement and in passing from each contact to its adjacent contact, while at the same time permitting the use of a comparatively large number of contacts. Another objectis to also secure a comparatively large capacity of the rheo stat by utilizing to the highest degree the space'available for the location of the resistance elements and the area from which heat may be dissipated. I accomplish this by arranging the'resistance contacts largely on a straight line, or upon the arc oi a circle having a comparatively large radius and locate a considerable number of the con tacts quite near the axis of the contact arm. This bringing of the resistance contacts, or a considerable portion of them, nearer the axis of the contact arm than in the case oi prior forms of construction, renders the remaining portion of the device available for the location of the resistance elements, or resistance conductors, giving maximum utilization of the device for that purpose while at the same time securing the advantage of a large angular movement of the contact arm to an extent of approximately 180, compared with about 30 of angular movement, in prior devices.

Another obj ectis to provide a contact arm of a character which when rotated will give proper contact with each of the resistance contacts in the successive positions of the Serial No. 431,628.

contact arm. Another object is to so position the location of the contacts in relation to the contact arm that the maximum number of contacts and resistance elements may be used, while at the same time scour-- ing a fairly uniform angular movement of: the contact arm in passing from one resistance contact to the adjacent one.

My invention is particularly well adapted for use with plate rheostats of rectangular outline, and by means of my invention such a plate is utilized very elliciently :tor the location of a maximum amount of the resistance conductor and for a maximum amount of surface for heat dissipation, while at the same time obtaining the advantage of a rotatable contact arm. Other objects and advantages of my invention will be understood from the following description and accompanying drawings, which illustrate one embodiment of my invention.

Fig. 1 is a rear elevation with some of he insulation broken away to show a portion of the resistance conductors.

Fig. 2 is a side View with the resistance plate in section, and Fig. 3 is a rear view or a portion of the rheostat showing the contact arm in one of its limiting positions.

A rectangular sheet metal plate 1 has an upturned edge, and has a layer or coating oi'- insulating material, on which are located the resistance conductors 2 connected to the resistance contacts 3. An insulating coating is applied over the resistance elements, or resistance conductors, and this coating is preferably an adhesive vitreous enamel, which effectively insulates and protects the conductors and holds them permanently in position, such construction being common in the art. In this instance the upper and lower half oi the plate are similarly provided with resistance conductors and con tacts.

The resistance contacts instead of being arranged on the arc of a circle are shown arranged on a straight line quite near the axis of the contact arm giving two parallelly arranged rows similarly located with respect to the axis of the contact arm. It will be noted however, that the contacts most distant from the center or" the plate are brought inwardly from the line of the other cont-acts forming a considerable angle therewith.

(ill

\Vith this arrangei'nent of contacts, it will be seen that the resistance conductors extend from quite near the middle of the plate to the outer edges and that all of the plate is utilized for the location of the resistance conductors, except a small middle portion, it being understood of course, that resistance conductors 2 extend from between each of the contacts 3 side by side over the full surface of the plate in a manner corresponding to the arrangement of the conductors shown in Fig. 1.

.\n insulated terminal 4 is mounted on the edge of the plate 1 from which a lead 5 passes to the contact 3 and the circuit is then continued through one set of resistance conductors and contacts to the contact 3*. Another insulated terminal 4: is mounted on the edge of plate 1 and a lead 5 extends to the contact 3 from which the circuit continues through the ther set of successive resistance elements and contacts to the contact 3 The two rows of contacts are bridged by a rotatable contact arm having an insulating handle 6 secured to the shaft '7. A bearing 8 for this shaft extends through an opening in the plate and is provided with side extensions S by which the bearing is supported. Screw bolts 8 pass through the extensions and the plate for securing the hearing in place. and the bearing bracket and bolts are suitably insulated from the plate as by insulation 9. Keyed to the shaft 7, but freely movable axially thereon. is a metal contact arm 10 preferably having contact strips 11 of low resistance metal such as copper, secured to the inner face of the contact arm, for engaging the fixed contacts It will be noted that the contact faces of the contact arm are quite elongated, the purpose of which is later explained.

Fixed to the outer end of the shaft 7 is a collar 12 having fixed thereto a plate 13 extending over the contact arm. The con tact arm has fixed thereto the pins H which pass freely through holes in the plate '13. Springs 15 are placed over the pins 14 and located between the plate 13 and the contact arm and serve to force the contact arm into firm engagement with the contacts 3 in any adjusted position of the rheostat. A collar 16 is fixed to shaft 7 in front of the bearing 8 for the purpose of holding the shaft against the pressure of the springs A stripof insulation 17 is secured to one edge the metal frame and supports a projecting part 18, such as a bolt, at the ends of two rows of contacts to serve as a stop for the contact arm in its limiting positions.

When the contact arm is in the position shown in Fig. 3, it engages the left-hand contact of the lower series and the righthand contact of the upper series, thus giving a direct connection between the terminals -land 4: with all resistance cut out. In this position the contact is made at the outer ends of the contact. arm. As the contact arm is turned, more resistance will evidently be included in the circuit, but in this progress from the osition shown in Fig. 3 to that shown in ig. l, the contact engagement of the contact arm with the successive contact buttons is gradually changed from the Outer ends of the contact arm to the portions of 76 the arm quite near its axis. As the movement is continued, the contact engagement again approaches the outer ends of the conact arm. Thus by providing the contact arm with elongated contact areas or sur- 80 faces, contact engagement is secured in any position of the arm with the contacts arranged as described. Also by means of the springs 15 being located over about the middle of each contact area on the arm 10, 86 a uniform and adequate contact is obtained between the arm and the fixed contacts in every position of the arm. It is evident that substantially all of the plate is effectively utilized vtor the location of the re- 00 sistance conductors, resulting in production of a rheostat having a comparatively large resistance capacity and a large surface area effective for the dissipation of heat. Likewise the advantage of a rotatable contact arm is obtained with a substantially uniform and large angular movement in pass; ing from one contact to the adjacent one, throughout the full range of adjustment.

Although T have described one embodiment of my invention, various modifications. may be made therein without departing from the scope thereof. My invention may be advantageously utilized with plates other than of rectangular shape and may in some 1 cases be utilized wit-h a contact arm having only one contact portion engaging a single row of contacts instead of the double arrangement above described; and the resisttance elements may be otherwise mounted and insulated than as above described.

I claim 1. A rheostat comprising a rotatable contact arm. a series of fixed contacts. and resistance elements connected to said contacts, a portionot said series of contacts being nearer the axis of said arm than another portion of said contacts.

2. A rheostat comprising a rotatable contact arm. a row of fixed contacts in a line extending from a point at a distance from. the axis of said arm to a point nearer the axis of said arm, and resistance elements connected to said contacts.

3. A rheostat comprising a rotatable contact arm, a row of fixed contacts having the middle portion of the row nearer the axis of said arm than the end portions of said row, and resistance elements connected to said contacts.

a. A rheostat comprising a rotatable contact arm, a row of fixed contacts arranged in approximately a straight line passing near the axis of said arm, and resistance elements connected to said contacts.

5. A rheostat comprising a rotatable contact arm, a row of fixed contacts arranged in approximately a straight line passing near the axis of said arm, and resistance elements connected to said contacts, said contact arm making engagement with said contacts over a variable area along the radius of said arm.

6. A rheostat comprising a rotatable contact arm, a row of fixed contacts arranged on an approximately straight line passing near the axis of said arm, and having the contacts which are located at the greater distance from said axis displaced inwardly from the general direction of said line, and resistance elements connected to said contacts.

7. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, and resistance elements mounted on said plate and con nected to said contacts, a portion of said contacts being nearer the axis of said arm than another portion of said contacts.

8. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, and resistance elements mounted on said plate and connected to said contacts, said row of contacts being arranged on a line having a portion of said line extending nearer the axis of said arm than another portion of said line.

9. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, and resistance elements mounted on said plate and connected to said contacts, said row of contacts being arranged on a line having the middle portion thereof nearer theaxis of said contact arm than the end portions of said line.

10, A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, and resistance elements mounted on said plate and con nected to said contacts, said row of contacts being arranged on a line having one portion extending near the axis of said contact arm and an outer portion turned inwardly "from the general direction of said line.

11. A rheostat comprising a supporting plate, a rotatable contact arm centrally located on said plate, two rows of fixed contacts supported by said plate approximately parallel to each other and on opposite sides of the axis of said arm respectively, a set of resistance elements supported on one portion oi said plate connected to one of said rows of contacts, and a second set of resistance elements supported on an opposed portion of said plate and connected to the other row of said contacts.

12. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, resistance conductors lying on the face of said plate and connected to said contacts and adhesive insulating material embedding said resistance conductors, said contacts being arranged on a line, a portion of said line being nearer the axis of said arm than another portion of said line of contacts.

18. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, resistance conductors lying on the face of said plate and connected to said contacts, and adhesive insulating material en'ibedding said resistance conductors, said row of contacts being arranged on a line having the middle portion thereof nearer the axis of said contact arm than the end portions of said line.

14. A rheostat comprising a supporting plate, a rotatable contact arm, a row of contacts mounted on said plate, resistance conductors lying on the face of said plate and connected to said contacts, and adhesive insulating material embedding said resistance conductors, said row of contacts being arranged on a line having one portion extending near the axis of said contact arm and an outer portion turned inwardly from the general direction of said line.

15. A rheostat comprising a supporting plate, a rotatable contact arm centrally located on said plate, two rows of fixed contacts supported by said plate approximately parallel to each other and on opposite sides of the axis of said arm respectively, a set of resistance conductors lying on the face of one portion of said plate connected to one of said rows or contacts, a second set of resistance conductors lying on the face of an opposed portion of said plate and connected to the other row of said contacts and adhesive insulating material on the face of said plate embedding said resistance conductors.

' LEONARD KEBLER. 

